Vocabulary- use CH 11 to define these terms. Homologous chromosomes Tetrad Crossing over Trait Gene Allele Hybrid Homozygous Heterozygous Phenotype Genotype Probability

Agenda 12/3- Cell Cycle Video clip: mitosis Review lab questions Quiz Meiosis vocabulary (due tomorrow)

Agenda 12/4- Meiosis Quiz Vocab squares- meiosis Notes- meiosis Modeling crossing over Sequencing mitosis and meiosis: compare and contrast

Eukaryotic Cell Division Mitosis- somatic (non-reproductive) cell division Parent cell divides into two identical daughter cells (diploid=2n) Meiosis- cell division resulting in reproductive cells (gametes) Parent cell divides into 4 daughter cells, each with half the number of chromosomes (haploid=1n) 5

Cell Division Humans have 46 chromosomes, 23 from each parent. Haploid cells: only one of each chromosome (n) Diploid cells: two of each chromosome (2n) 6

Why don’t you look exactly like your parents or siblings? Meiosis! Instead of 2 cells that are identical to the parent cell, as in mitosis, meiosis results in 4 haploid cells that are different from the parent cell and from each other.

Why don’t you look exactly like your parents or siblings? Meiosis! Sexual reproduction increases genetic variation in a population, which increases a species’ ability to adapt to changes in their environment.

Sexual Reproduction Male gamete (sperm) and female gamete (egg) are haploid (1n) Fertilization occurs when an egg and a sperm fuse to form a zygote (2n). Meiosis is the form of cell division that results in gametes.

Meiosis produces gametes 4 haploid daughter cells formed Preceded by interphase and DNA replication 2 divisions Meiosis I Meiosis II 10

Meiosis- click for video clip Meiosis I- like mitosis but only one copy of each homologous chromosome goes to each new cell; two new cells formed Prophase I Metaphase I- homologous chromosomes line up on equator Anaphase I- homologous chromosomes separate Telophase I- two new cells, each with half the genetic material Meiosis II- the two cells formed in Meiosis I divide again Basically like Mitosis 11

The Human Karyotype Homologous Chromosomes chromosome pair, one from each parent, that are similar in length, gene position and centromere location

Meiosis I - Reduction Division Interphase I Prophase I Metaphase I Anaphase I Each chromosome pairs with its corresponding homologous chromosome to form a tetrad. Cells undergo a round of DNA replication, forming duplicate Chromosomes. Homologous chromosomes line up along the middle of the cell. Spindle fibers attach to the chromosomes. The fibers pull the homologous chromosomes toward the opposite ends of the cell.

Meiosis I - Reduction Division Interphase I Prophase I Metaphase I Anaphase I Crossing over- exchange of genetic info between homologous chromosomes- increases genetic variation among offspring Cells undergo a round of DNA replication, forming duplicate Chromosomes. Homologous chromosomes line up along the middle of the cell. Spindle fibers attach to the chromosomes. The fibers pull the homologous chromosomes toward the opposite ends of the cell. This reduces the chromosome number in each daughter cell by half.

Meiosis II - Similar to Mitosis Prophase II Metaphase II Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original. The chromosomes line up in a similar way to the metaphase stage of mitosis. Anaphase II Telophase II The sister chromatids separate and move toward opposite ends of the cell. Meiosis II results in four haploid (N) daughter cells.

Modeling Crossing Over Use paper strips to create a model of crossing over First, create a pair of homologous chromosomes using two different colors. Replicate the DNA and hold the sister chromatids together with a paper clip or tape Materials: scissors, tape, construction paper

Agenda 12/5- Meiosis Bellwork- sequencing mitosis and meiosis Notes- comparing mitosis and meiosis Video- Life’s Greatest Miracle Homework- study for unit test (DNA structure and replication, cell cycle, cell division- mitosis and meiosis)

Mitosis vs. Meiosis Animation Mitosis- 2 diploid cells produced Meiosis- 4 haploid cells produced Why? 18

Meiosis Using two successive divisions to reduce the number of chromosomes by half and create gametes. Homologous chromosomes: a pair of chromosomes with the same genes (but may have different alleles); one from each parent.

Mitosis vs. Meiosis Mitosis Meiosis 1 2 4 46 (diploid) 23 (haploid) # of divisions 1 2 # of daughter cells produced 4 # chromosomes in parent cell 46 (diploid) # chromosomes in daughter cell 23 (haploid) Type of cells produced Somatic (body) cells Gametes (sex cells)

Life’s Greatest Miracle Video link Answer the questions on the worksheet

Comparing Mitosis and Meiosis Place the cards in order How are the two processes similar? How are they different?

Chromosomes and Genes Traits are inherited through genes on chromosomes. Chromosomes are composed of several hundred to a few thousand genes. A genes specific location on a chromosome is called a locus (pl. loci).